Dorsal digital septum of the distal interphalangeal joint.

Abstract

Clinical observation has led to the discovery of a distinct anatomic septum from the extensor tendon to the skin at the distal phalanx that appears to limit the proximal spread of infection from the dorsum of the distal phalanx. This study employed histology and high-resolution magnetic resonance imaging (MRI) to identify this anatomic structure at the level of the distal interphalangeal (DIP) joint. We used high-resolution (16.4-T) MRI to image and section 10 cadaveric fingers (9 female, 1 male) from both left and right hands. Once imaged, we made histologic sections using hematoxylin and eosin, or Van Gieson's stain, and examined them microscopically for concordant findings. In all 10 scans, the proposed septum was visualized using MRI with histologic confirmation. It was observed to extend from the skin creases overlying the dorsal aspect of the DIP joint to the extensor tendon. It is composed of collagen bundles arranged in a variable network that adhere extensor tendon to skin at the DIP joint. Clinical observations proposed the existence of a distinct septum between extensor tendon and skin at the level of the DIP joint. We confirmed this structure to be a collagen septum by MRI and histology. This previously undescribed structure is called the dorsal septum.